Cellular apoptosis and proliferation in testes of fathead minnow exposed to wastewater treatment plant effluent
Environmental toxicants and their effects on both wildlife and human populations have become more concerning as worldwide human populations grow, water sources become scarce, and anthropogenic waste becomes more prevalent. Municipal wastewater treatment plants (WWTPs) are designed to conserve water by removing nutrients and pathogens from wastewater and release effluent water back into local streams. Unfortunately, many wastewater compounds are not completely removed from the effluent and are released into the environment, sometimes causing deleterious effects even in minute quantities on biological life. Testing of anthropogenic compounds and effects on wildlife was conducted at the City of Boulder WWTP in 2005, 2006, 2008, and 2011. Biological assays were performed by maintaining adult male fathead minnow in either reference or effluent water for 28 days, and by measuring secondary sex characteristics, plasma vitellogenin, and gonad histology. It was found that significant disruption in gonad weight, sperm abundance, and vitellogenin occurred in effluent exposed fish in 2005, but little or no significant disruption occurred in any later year because of a major WWTP upgrade that improved effluent water chemistry. The aim of this study was to examine biological effects further by testing for discrete cellular changes of the same experimental fish from 2005, 2006, and 2008. This approach involved analyzing biomarkers, which identified cellular proliferation via proliferating cell nuclear antigen (PCNA) and apoptosis via terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL). It was found that epithelial PCNA was higher in effluent-exposed fish in 2005 only, but was lower in sperm cells of effluent fish in 2006, and higher in sperm of reference fish in 2005 and 2008 (p<0.05). Epithelial and sperm TUNEL was greater in effluent exposed fish in 2005 and 2006 (p<0.05), but was not significantly different in 2008. PCNA was found to be inconsistent between years, but TUNEL was consistent with previous measurements, proved to be a more reliable biomarker, and showed that disruption is still occurring in 2008 fish even after the WWTP upgrade. Future use of TUNEL is recommended, as it responds to discrete cellular disruption early and shows disruption when other measurements fail to respond.
Book contributor Auraria Library
Collection auraria; additional_collections